Persuasion is a form of social influence. It is the process of guiding people toward the adoption of an idea, attitude, or action by rational and symbolic (though not only logical) means. It is a problem-solving strategy, and relies on "appeals" rather than force.

Dissuasion is the process of convincing someone not to believe or act on something.

Persuasion is often confused with manipulation, which is the act of guiding another towards something that is not in their best interest by subverting their thought processes. Persuasion is meant to benefit all parties in the end.

Aristotle says that "Rhetoric is the art of discovering, in a particular case, the available means of persuasion."

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Attitudes can be changed through persuasion. The celebrated work of Carl Hovland, at Yale University in the 1950s and 1960s, helped to advance knowledge of persuasion. In Hovland's view, we should understand attitude change as a response to communication. He and his colleagues did experimental research into the factors that can affect the persuasiveness of a message:

1. Target Characteristics: These are characteristics that refer to the person who receives and processes a message. One such trait is intelligence - it seems that more intelligent people are less easily persuaded by one-sided messages. Another variable that has been studied in this category is self-esteem. Although it is sometimes thought that those higher in self-esteem are less easily persuaded, there is some evidence that the relationship between self-esteem and persuasibility is actually curvilinear, with people of moderate self-esteem being more easily persuaded than both those of high and low self-esteem levels (Rhodes & Woods, 1992). The mind frame and mood of the target also plays a role in this process.

2. Source Characteristics: The major source characteristics are expertise, trustworthiness and interpersonal attraction or attractiveness. The credibility of a perceived message has been found to be a key variable here (Hovland & Weiss, 1951); if one reads a report about health and believes it came from a professional medical journal, one may be more easily persuaded than if one believes it is from a popular newspaper. Some psychologists have debated whether this is a long-lasting effect and Hovland and Weiss (1951) found the effect of telling people that a message came from a credible source disappeared after several weeks (the so-called "sleeper effect"). Whether there is a sleeper effect is controversial. Received wisdom is that if people are informed of the source of a message before hearing it, there is less likelihood of a sleeper effect than if they are told a message and then told its source.

3. Message Characteristics: The nature of the message plays a role in persuasion. Sometimes presenting both sides of a story is useful to help change attitudes.

4. Cognitive Routes: A message can appeal to an individual's cognitive evaluation to help change an attitude. In the central route to persuasion the individual is presented with the data and motivated to evaluate the data and arrive at an attitude changing conclusion. In the peripheral route to attitude change, the individual is encouraged to not look at the content but at the source. This is commonly seen in modern advertisements that feature celebrities. In some cases, physician, doctors or experts are used. In other cases film stars are used for their attractiveness.

According to Robert Cialdini in his book on persuasion, he defined six "weapons of influence":[1]

Reciprocation - People tend to return a favor. Thus, the pervasiveness of free samples in marketing. In his conferences, he often uses the example of Ethiopia providing thousands of dollars in humanitarian aid to Mexico just after the 1985 earthquake, despite Ethiopia suffering from a crippling famine and civil war at the time. Ethiopia had been reciprocating for the diplomatic support Mexico provided when Italy invaded Ethiopia in 1937.

Commitment and Consistency - Once people commit to what they think is right, orally or in writing, they are more likely to honor that commitment, even if the original incentive or motivation is subsequently removed. For example, in car sales, suddenly raising the price at the last moment works because the buyer has already decided to buy. See cognitive dissonance.

Social Proof - People will do things that they see other people are doing. For example, in one experiment, one or more confederates would look up into the sky; bystanders would then look up into the sky to see what they were seeing. At one point this experiment aborted, as so many people were looking up that they stopped traffic. See conformity, and the Asch conformity experiments.

Authority - People will tend to obey authority figures, even if they are asked to perform objectionable acts. Cialdini cites incidents, such as the Milgram experiments in the early 1960s and the My Lai massacre.

Liking - People are easily persuaded by other people whom they like. Cialdini cites the marketing of Tupperware in what might now be called viral marketing. People were more likely to buy if they liked the person selling it to them. Some of the many biases favoring more attractive people are discussed. See physical attractiveness stereotype.

Scarcity - Perceived scarcity will generate demand. For example, saying offers are available for a "limited time only" encourages sales.

Propaganda is also closely related to Persuasion. Its a concerted set of messages aimed at influencing the opinions or behavior of large numbers of people. Instead of impartially providing information, propaganda in its most basic sense presents information in order to influence its audience. The most effective propaganda is often completely truthful, but some propaganda presents facts selectively to encourage a particular synthesis, or gives loaded messages in order to produce an emotional rather than rational response to the information presented. The desired result is a change of the cognitive narrative of the subject in the target audience. The term 'propaganda' first appeared in 1622 when Pope Gregory XV established the Sacred Congregation for Propagating the Faith. Propaganda was then as now about convincing large numbers of people about the veracity of a given set of ideas. Propaganda is as old as people, politics and religion.